When political advisors want to know their candidate's chances in an upcoming election, they sample the potential voting population rather than querying the whole group. When researchers in counseling, therapy, social psychology, developmental psychology, education, and communication want to study the patterns of interaction in human groups, they typically record a segment of that interaction in the laboratory or in the field. That segment is usually coded for the presence or absence of a variety of nonverbal and vocal behaviors as indicators of various internal psychological states. The financial, human and logistical costs of coding these microscopic behaviors is "solved" by recording only relatively brief segments of the interaction or coding single behaviors over longer periods. The alternative of sampling relatively lengthy interaction records has not been systematically explored. The research proposed here will develop an archive of 48 one-half hour interactions among all possible combinations of established and newly formed pairs, highly expressive and inexpressive pairs, liking and disliking pairs, in all combinations of same and opposite sex pairings. This archive will be coded in its entirety for a number of nonverbal and vocal (but not verbal) behaviors. Each of the 48 interactions will be sampled with finer and grosser sampling units and at greater and lesser percentages of the total interaction duration. Each sample will be compared to the total interaction in terms of the mean for that behavior overall as well as for the sequential structure for that behavior. The sampling procedure will be considered successful if the association between sample measures and total measures is high relative to the costs for coding that sample. If the sampling procedure can be shown to be valid, then interactions can be allowed to continue for longer and therefore more representative durations and researchers and therapists can code a multiplicity of behaviors without incurring crippling burdens in the costs of archiving and coding behaviors. In fact, a successful sampling validation permits the development of a video recording-computer driven unit that records only samples of the interaction. Such a device would permit significant economies in the use of videotape and film for archives while permitting long interactions to evolve naturally.